System for synchronizing master and secondary timers



Aug. 28, 1956 w. M. JEFFERS SYSTEM FOR SYNCHRONIZING MASTER AND SECONDARY TIMERS Filed Jan. 27, 1954.

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United States Patent C SYSTEM FOR SYNCHRONIZING MASTER AND SECONDARY TIMERS Walter M. Jeifers, Syracuse, N. Y., assignor to Crouse- Hinds Company, Syracuse, N. Y., a corporation of New York Application January 27, 1954, Serial No. 406,554 2 Claims. (Cl. 318-75) This invention has to do with a system for synchronizing a secondary timer with a master timer. For example, in certain traflic signaling systems, it is conventional practise to maintain a plurality of secondary signal timers controlling the trafiic signals at a plurality of street intersections in the system so that each secondary timer opcrates in a predetermined phase relation with the other timers in the system. This relation is brought about by various arrangements and there is usually provided a master timer having supervisory control over the secondary timers, whereby the secondary timers are maintained in synchronism or if one or more of the secondary timers should get out of synchronism, or out of step, the master timer functions to get the secondary timer, which is out of step, back into step with the system.

In such systems, it is common practise to provide an arrangement whereby each secondary timer will, if it becomes out of step, dwell for a period of time until it is in step or synchronism with the master timer, whereupon it will be released and then operate in synchronism with the master. Such an arrangement is disclosed in Patent No. 1,946,436, issued February 6, 1934, to C. H. Bissell. It sometimes happens that the secondary timer gets out of step with the master timer to such an extent that the secondary timer dwells for substantially the entire cycle length of the master timer. In tratlic signaling systems, this excessively long dwell means that traffic on one street of the intersection is held up for the long period of time, resulting in a trafiic tie-up which often upsets the desired flow of traflic over an extended period of time. Various arrangements have heretofore been proposed whereby the maximum dwell of the secondary timer is controlled or reduced to some fractional part of the cycle of the master timer. However, these prior arrangements have involved complicated apparatus, expensive to construct, and which required considerable maintenance.

This invention has as an object a greatly simplified arrangement whereby the maximum length of time the secondary timer dwells is only a fractional part of the length of the master timer cycle and which requires a modification of the master timer which may be economically effected and which does not add to the expense of maintaining the apparatus.

The invention consists in the novel features and in the combinations and constructions hereinafter set forth and claimed.

In describing this invention, reference is had to the accompanying drawings in which like characters designate corresponding parts in all the views.

Figure 1 is a diagrammatic view of a synchronizing apparatus embodying my invention.

Figure 2 is a chart illustrating the contact progression when the secondary timer is in the process of being synchronized with the master.

Figure 3 is a chart, similar to Figure 2, but wherein the contacts under the control of the progressor dial are positioned in different phase relation to the master timer than in the chart shown in Figure 2.

Referring to Figure 1, the master timer is designated at 10, and the secondary timer at 11. The master timer includes a dial 12 rotated through repeated cycles by a motor 13 having a driving coil 14. The secondary timer is provided with a dial 15 rotated through repeated cycles by a motor 16 having a driving coil 17. The motors 13, 16, are of the synchronous type, or otherwise efiect rotation of the dials 12, 15, at uniform speed, whereby the dials have cycles of equal length.

The secondary timer 11 is provided with means for stopping or disabling its operation. As here shown, the motor 16 is provided with a brake coil 20 which is operable, when energized, to stop the motor 16. The coil 20 is energized by a circuit including normally open contacts 21 associated with the dial 15, normally closed contacts 22 associated with the dial 12, and normally open contacts 24 associated with a dial 25'. The dial 25 forms part of the master timer 10 and is connected to the dial 112 by positive drive means, such as the chain 26 and sprockets 27, 28, this drive arrangement being operable to effect rotation of the dial 25 at a speed slower than that of the dial 12.

The dials 12 and 15 are provided respectively with switch actuating members 29, 30, which function to actuate the contacts 21, 22, once during each rotation of these dials, this actuation being momentary.

The dial 25 is provided with an actuator 31 in the form of a cam lobe which functions to close the contacts 24 once during each cycle of the dial 25, this closure being for a substantial period. The cam actuator 31 must be at least long enough to close the progressor contacts 24 for a period of time at least equal to the difference between the base cycle of the master dial 12 and the cycle of the progressor dial 25. For example, if the master and secondary dials 12, 15, are being rotated one revolution in forty seconds and it is desired to have the secondary dial dwell for a period, not to exceed ten seconds, the drive connection between the master dial 12 and the progressor dial 25 is such that the progressor dial takes at least ten seconds longer to complete one revolution or cycle. In this case, the maximum dwell desired is 25% of the cycle of the master and secondary dials. Accordingly, the progressor dial should have its cycle increased by 25% over the master and secondary dials, whereby the progressor dial would make one revolution in fifty seconds. The cam actuator 30 is then made of a length sufficient to close the contacts 24 for at least a ten second period during the fifty second cycle of the progressor dial.

The chart, Figure 2, shows the contact closure during movement of the master dial through ten cycles of opera tion. The closure of the contacts 22 is shown by heavy lines 32. The closure of contacts 24 is shown by heavy lines 34. The closure of contacts 21 is shown by heavy lines 36.

In the chart, Figure 1, the contacts 24 of the progressor dial are shown closed, as at 34, during the initial part of the cycle. The secondary dial 15 is shown displaced or out of synchronism to the extent that its contacts 21 close at substantially the midpoint of the cycle of the master dial. With this phase relation existing between the dials, it will be observed that in the second cycle the contacts 24 are closed at a later interval than in the first cycle this, due to the fact that the progressor dial is rotating at a slower speed than the master dial. Accordingly, the contacts 24 are closed at successively later parts of the cycle of the master dial. In the third cycle, the closure of the contacts 24 overlap the closure of the secondary timer contacts 21, whereby all of the contacts 21, 22, 24, are now closed, completing the circuit to the braking coil 20; causing the secondary timer 15 to dwell for the period during which the contacts 24' are closed. This results in shifting the phase relation between the secondary dial 1S and the master dial 12 to an extent equal to the closure of the contacts24, whereby in the fourth cycle the secondary contacts 21 again close simultaneously with the contacts 24, effecting a further dwell of the secondary timer and, at the end or" this dwell, the secondary timer is released with its actuator in the same phase relation as the actautor 29 on the master dial 12', whereupon the dial i is now in step or synchronism with the dial 12. It will be observed that starting with the arrangement shown in Figure 1 at the'left end of the chart, Figure 2, the secondary dial has dwelled only during thethird and fourth cycles, and each of those dwells was in duration only twenty-five percent of the base master cycle.

In the chart, Figure 3, the master and secondary dials start out in the same phase relation as existed in the ar rangement shown in Figure 2. However in Figure 3, the progressor dial is illustrated as being positioned to close its contacts 24 at the midpoint of the cycle rather than at the beginning of the cycle. With this situation, the master contacts 22 and the progressor contacts 24 are both closed during the closure of the secondary contacts 21, effecting a dwell for the remainder of the period during which the progressor contacts are closed. In the second cycle, the contacts 21, 24, will close simultaneously, effecting a dwell of the secondary timer during the entire period the contacts 2 are closed. In the third cycle, the actuator 31 has shifted to its position so that the contacts 24 are closed for a period overlapping the opening of the contacts 22 and inasmuch as the progressor dial and the secondary dial 15 are now operating in synchronisrn, the secondary dial 15 will be released by the opening of the contacts 22 at the beginning of the master cycle and thereafter, the secondary dial will operate in step with the master dial. In this situation, the secondary dial has dwelled for a short period in the first cycle, the maximum period in the second cycle, and a short period in the third cycle, whereupon it has reached synchronism with the master dial.

In the system disclosed, the secondary timer is brought into synchronism with the master timer and this is accomplished by a succession of short dwell periods. These dwell periods may be formed of any desired length, it only being necessary that the speed of the progressor dial 25 and the length of its cam 31 be proportioned so that the progressor contacts 24 are closed for a period at least as long as the difference between the cycle lengths of the master and progressor dials. This arrangernent only necessitates the addition of the progressor dial at the master timer and the contacts 24 op- .4 erated thereby, thus not adding materially to the cost of the master timer, or to the maintenance of the same.

What I claim is:

1. A system for synchronizing a secondary timer with a master timer, motors for operating said timers respectively through cycles of equal duration, an electro-responsive stopping brake for the secondary timer, a circuit for operating said brake including a normally open contact closed once during each cycle of the secondary timer, a normally closed contact opened once during each cycle of said master timer, and a third normally open contact closed once during each cycle of the master timer, all of said contacts being connected in series with said brake and said first and second contacts being operated momentarily, said third contact being closed by a cam associated with the master timer, means" for rotating said cam at a speed to give a cycle having a duration greater than the cycle of said master and secondary timers, said cam being of suificient lengthto close said third contact for a period having a duration at least equal to the difference between the duration of the cycles of the master and secondary timers and the cycle of said cam.

2. A- system for synchronizing a secondary timer with a master timer, amaster timer dial, a secondary timer dial and a progressor dial, a motor operatively connected toeach of said master and secondary dials, said motors effecting rotationof said dials at the same speed in cycles of equal length, an electro-responsive brake associated with the'secondary dial motor and operable when energized to stop said motor, positive drive means connecting said master dial to said progressor dial at a reduced speed togivea cycle of greater length, a normally open switch associated with said progressor dial, a normally closed switch associated with said master dial, and'a normallyopen'switch associated with said secondary dial, said switches being connected in series circuit with the braking'coil, said master and secondary dials being provided with switch actuating members operable to momentarily actuate the switches associated with said dials once during each cycle of said dials, said progressor dial having a switch actuator operable to close its associated'switch once during each cycle of said progressor dial for aperiod at least equal to the difference between the master and progressor' dial cycle lengths.

ReferencesCited in the file of this patent UNITED STATES PATENTS 1,874,513 Hall Aug. 30, 1932 1,934,786 Bissell Nov. 14, 1933 2,036,983 Ryan Apr. 7, 1936 2,228,079 Gulliksen Jan. 7, 1941 

